A variety of luminescent compounds are known in the art. Green and red luminscent compounds are not uncommon, but blue luminescent metal ions and molecules are rare and generally expensive.
Two types of blue luminescent inorganic coordination compounds are known in which a heterocyclic chromophore includes a metal center coordinated by nitrogen and oxygen atoms of organic ligands. One type is based on 8-hydroxyquinoline and derivatives thereof, and the other is based on azomethine and derivatives thereof. Both the 8-hydroxyquinoline- and azomethine-based systems usually require several steps of synthesis and modification in order to achieve blue luminescence. The usefulness of these two systems in practical electroluminescence applications is limited, and blue luminescent materials with improved properties are desirable.
Production of devices based on electroluminescent display, and in particular on flat panel display, is a rapidly growing, billion dollar industry. Blue luminescent materials, as one of the key color components for electroluminescence display devices, are among the most sought-after materials by industry around the world.